A greedy gobbling galaxy has been caught in the act - noshing on its neighbors and leaving crumbs of evidence about its dietary past.
Galaxies grow by churning loose gas from their surroundings into new stars, or by swallowing neighboring galaxies whole. However, they normally leave very few traces of their cannibalistic habits.
A study published in the Monthly Notices of the Royal Astronomical Society (MNRAS) not only reveals a spiral galaxy devouring a nearby compact dwarf galaxy, but shows evidence of its past galactic snacks in unprecedented detail, according to a press release.
Australian Astronomical Observatory (AAO) and Macquarie University astrophysicist, ángel R. López-Sánchez, and his collaborators have been studying the galaxy NGC 1512 to see if its chemical story matches its physical appearance. The team of researchers used the unique capabilities of the 3.9-meter Anglo-Australian Telescope (AAT), near Coonabarabran, New South Wales, to measure the level of chemical enrichment in the gas across the entire face of NGC 1512.
"We were expecting to find fresh gas or gas enriched at the same level as that of the galaxy being consumed, but were surprised to find the gases were actually the remnants of galaxies swallowed earlier," López-Sánchez said, according to the press release. "The diffuse gas in the outer regions of NGC 1512 is not the pristine gas created in the Big Bang but is gas that has already been processed by previous generations of stars."
"The dense pockets of hydrogen gas in the outer disk of NGC 1512 accurately pin-point regions of active star formation," said CSIRO's Baerbel Koribalski, a member of the research collaboration, according to the press release.
Tobias Westmeier, from the International Centre for Radio Astronomy Research in Perth, said that while galaxy cannibalism has been known for many years, this is the first time that it has been observed in such fine detail.
"By using observations from both ground- and space-based telescopes we were able to piece together a detailed history for this galaxy and better understand how interactions and mergers with other galaxies have affected its evolution and the rate at which it formed stars," he said, according to the press release.
Reference:
"Ionized Gas in the XUV Disc of the NGC 1512/1510 System," á. R. López-Sánchez, T. Westmeier, C. Esteban, and B. S. Koribalski, Monthly Notices of the Royal Astronomical Society (MNRAS), 11 July 2015, Vol. 450, No. 4 [https://mnras.oxfordjournals.org/content/450/4/3381].
